As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED THAT DURING CLIMB RECEIVED A LANDING GEAR AIR/GROUND FAIL MESSAGE ON THE EICAS. THE CREW RETURNED TO KLGA AND LANDED WITHOUT INCIDENT. MAINTENANCE REPORTED, CMC MESSAGE FOR LGEU FAIL. REPLACED THE LGEU AND PERFORMED LANDING GEAR SWINGS. OPERATIONAL CHECKS OF THE LANDING GEAR EXTENSION AND RETRACTION SYSTEM WERE GOOD WITH NO FURTHER DEFECTS NOTED.